The perils of a cashless society were exposed yesterday as a technology blunder triggered 'the world's biggest IT meltdown'.

In what was dubbed a 'digital pandemic', a glitch in a software update sparked global chaos as computers crashed in shops, banks and hospitals.

Train ticket machines seized up, GP surgeries were forced to cancel appointments and planes were grounded in multiple countries.

Waitrose and Morrisons were among the supermarkets unable to take card payments for a time – meaning customers who no longer carry cash could not buy food.

Critics said the havoc showed the dangers of a cashless world, with almost half of Britons now leaving the house with only their phones as a means of payment.

The aftermath of the disruption, which was caused by a bug affecting Microsoft Windows, is predicted to last for four days.

Among the chaos yesterday:

• Millions of patients were unable to book GP appointments;
• One hospital declared a 'critical incident' as it was forced to cancel cancer treatments;
• Departure boards went blank at airports including Heathrow, Gatwick and Edinburgh on the busiest day for UK air travel since 2019;
• Stock markets slid in London, New York, Paris and Frankfurt;
• Sky News and CBBC were among broadcasters knocked offline;
• Emergency 911 phonelines went down in several US states while shops in Australia were forced to shut early;
• Security systems at the Paris Olympics froze – just one week before the opening ceremony;
• Business leaders warned wages could be delayed by payroll system problems.

Other firms affected included McDonalds, Barclays and British Airways. The Mercedes F1 team also said it was working to fix any issues ahead of the Hungarian Grand Prix.

Chris Dimitriadis, a cyber-security expert at IT association Isaca, said: 'This incident is a clear example of what could be termed a digital pandemic, a single point of failure impacting millions of lives globally.'

Experts said yesterday's disruption was on the scale expected from the 'Y2K Millennium Bug' – a computer meltdown forecast as the year changed from 1999 to 2000 which never materialised.

Troy Hunt, a respected security consultant, said: 'I don't think it's too early to call it: this will be the largest IT outage in history. This is basically what we were all worried about with Y2K, except it's actually happened this time.'

Both China and Russia claimed to have been unaffected, with Moscow boasting of its 'increased self-sufficiency'.

Some office workers shared jokes about their working week ending early, posting on social media: 'Happy weekend, thank you Microsoft!'

But the instant collapse of Microsoft Windows – the most popular operating system in the world – prompted warnings Britain would be woefully unprepared if there was a major cyber-attack. Experts said it was a wake-up call because, if hostile nations ever inflict a well-planned IT assault, the consequences could be far worse.

Dennis Reed, director of the Silver Voices campaign group which represents older people, said: 'It's extremely worrying. This should be a big warning for the Government. Obviously it has affected older people particularly, not just with the cash side of things but GP appointments and everything else.

'If people can't pay because they can't use their phone then when systems go down – and they always will – people won't be able to access vital services, food, and the essentials of life.

'With this ever-more digital society, we are reliant on it all working. But we have no control over it. We are putting all our eggs in one basket. The future security of the nation is in danger.'

Martin Quinn, campaign director at the Payment Choice Alliance, told The Daily Telegraph: 'With IT outages happening now at alarming regularity, businesses should be mindful of only taking card payments.

'However many supermarkets prefer to have self-service card-only tills, which makes cash users feel like second-class citizens, a concerted effort is needed to return to using and accepting cash, because cash never crashes.'

Britain is fast becoming a cashless society, with an estimated 25 million over-16s – 45 per cent of Britons – saying they do not take their wallets with them when heading out. It has also become harder to take out cash, with 23,000 cash machines expected to shut down by 2030.

The Government's emergency committee Cobra met under the lead of the Chancellor of the Duchy of Lancaster, Pat McFadden, to manage the response to the outage. 

US cyber-security firm CrowdStrike said it was responsible for the mayhem, which started yesterday morning, after sending a 'defective' update to machines running Microsoft apps.

Chief executive George Kurtz said the glitch was 'not a security incident or cyber-attack'. But he said he was 'deeply sorry for the impact that we've caused' and warned it would take 'some time' for systems to be fully restored.

Microsoft has suggested customers try rebooting their computers 15 times to resolve the issue.